Slime control for primary filtration systems

Abstract

A process and apparatus for protecting a media bed filter with underlying support screen from solids contained in a liquid, such as filtrate from the filter, used to regenerate or backwash the media bed filter. Filtrate enters a first collection chamber containing a screen assembly covering one outlet, the chamber also containing a second outlet. Filtrate traverses the screen assembly and is transferred to a second collection chamber with addition of a predetermined amount of bactericide to prevent solids growth therein. Upon bactericide-treated filtrate reaching a predetermined level within the second chamber, filtrate in the first chamber bypasses the screen assembly and flows out the second output to further biological treatment or use. Bactericide-treated filtrate from the second collection chamber is used to regenerate or backwash the media bed filter with addition of optional surfactant to assist in cleaning the filter media and underlying support screen. The first collection chamber has an alarm system which detects resistance of filtrate flow traversing the screen assembly and warns that the screen assembly requires cleaning or replacement, thus fully protecting the support screen from solids.

I claim: 
     
       1. A process for control of the quality of a media bed filter regenerating or backwashing liquid, to protect the filter bed media and the media support structure from the deleterious effects of biological solids generated or retained within said liquid comprising the steps of; (a) introducing a filtrate from said media bed filter into a first collection chamber containing a removable screen assembly covering a first upper outlet, said chamber also containing a second lower outlet;   (b) transferring filtrate which has traversed said screen assembly in said first collection chamber to a predetermined level within a second collection chamber;   (c) adding a predetermined amount of bactericide to said filtrate which has traversed said screen assembly to retard bacterial growth therein, to form a bactericide-treated filtrate; and   (d) regenerating or backwashing said media bed filter with said bactericide-treated filtrate to improve operation of said filter.   
     
     
       2. A process according to claim 1 comprising the additional step of; (e) bypassing said screen assembly, with said filtrate flowing through said second lower outlet in said first collection chamber, upon said bactericide-treated filtrate reaching said predetermined level within said second collection chamber.   
     
     
       3. A process according to claim 2 wherein said filtrate from said second outlet in step (e) receives further biological treatment. 
     
     
       4. A process according to claim 1 wherein said bactericide is a solution of sodium hypochlorite. 
     
     
       5. A process according to claim 1 wherein said transferring step (b) is by overflowing said filtrate from said first collection chamber to said second collection chamber. 
     
     
       6. A process according to claim 5 wherein said predetermined amount of bactericide added to said filtrate in step (c) is determined by measuring the overflow rate of filtrate from said first collection chamber to said second collection chamber. 
     
     
       7. A process according to claim 5 wherein said predetermined amount of bactericide in step (c) is added to the filtrate in a mixing zone prior to the filtrate entering said second collection chamber. 
     
     
       8. A process according to claim 5 wherein said predetermined amount of bactericide in step (c) is added to said filtrate within said second collection chamber. 
     
     
       9. A process according to claim 1 wherein said transferring step (b) is by pumping the filtrate from within said screen assembly from said first collection chamber to said second collection chamber. 
     
     
       10. A process according to claim 9 wherein said predetermined amount of bactericide added to said filtrate in step (c) is determined by the rate of pumping of filtrate from said first collection chamber to said second collection chamber. 
     
     
       11. A process according to claim 10 wherein said predetermined amount of bactericide and said filtrate flow through mixing means prior to the bactericide-treated filtrate entering said second collection chamber. 
     
     
       12. A process according to claim 1 wherein said regenerating or backwashing step (d) is by pumping said bactericide-treated filtrate from said second collection chamber. 
     
     
       13. A process according to claim 1 wherein a predetermined amount of a surfactant is added to said bactericide treated filtrate in regenerating or backwashing step (d) to assist in regenerating said media bed filter. 
     
     
       14. A process according to claim 13 wherein said surfactant is a detergent. 
     
     
       15. A process according to claim 1 wherein a resistance to said filtrate traversing said screen assembly in said first collection chamber in step (b) produces an alarm signal. 
     
     
       16. A process according to claim 15 wherein said alarm signal is produced by a first filtrate level exterior said screen assembly within said first chamber activating a level switch at a predetermined level exceeding a second filtrate level overflowing from said first chamber to said second chamber. 
     
     
       17. A process according to claim 15 wherein said alarm signal is produced by a first filtrate level exterior said screen assembly within said first chamber exceeding a third filtrate level within said screen assembly by a predetermined distance. 
     
     
       18. An apparatus for control of the quality of a media bed filter regenerating or backwashing liquid, to protect the filter bed media and the media support structure from the deleterious effects of biological solids generated or retained within said liquid comprising; a first collection chamber with a liquid inlet; a first liquid outlet containing a removable screen assembly; a second liquid outlet located below the level of said first liquid outlet; a second collection chamber; means for transferring liquid which has traversed said screen assembly to said second collection chamber; means for measuring the amount of liquid transferred from said first collection chamber to said second collection chamber; means for adding a predetermined amount of bactericide to said liquid entering said second collection chamber; control means for terminating transfer of liquid from said first chamber to said second chamber upon the liquid in said second chamber reaching a predetermined level; and means to deliver a bactericide-treated liquid to said media bed filter to regenerate or backwash said filter.   
     
     
       19. An apparatus according to claim 18 wherein said removable screen assembly is a rectangular box metalwork frame with a screen material mounted on four vertical sides and bottom of said frame, with an open top which fits securely within said first liquid outlet. 
     
     
       20. An apparatus according to claim 19 wherein said screen material contains openings no larger than the openings of a screen supporting the filter bed media. 
     
     
       21. An apparatus according to claim 19 wherein said screen material contains openings smaller than the openings of a screen supporting the filter bed media. 
     
     
       22. An apparatus according to claim 18 wherein said means for transferring liquid which has traversed said screen assembly to said second chamber is a valve which closes said second outlet in said first chamber causing liquid to overflow into said second chamber. 
     
     
       23. An apparatus according to claim 18 wherein said means for transferring liquid which has traversed said screen assembly to said second chamber is a pump with intake located within said screen assembly. 
     
     
       24. An apparatus according to claim 22 wherein said means for measuring liquid transferred to said second chamber is an ultrasonic device to measure the height of liquid level overflowing said first chamber to said second chamber. 
     
     
       25. An apparatus according to claim 23 wherein said means for measuring liquid tranferred to said second chamber is a control for said pump with intake located within said screen assembly. 
     
     
       26. An apparatus according to claim 18 wherein said means for adding a predetermined amount of bactericide to liquid entering said second chamber is a pump. 
     
     
       27. An apparatus according to claim 18 wherein said control means for terminating transfer of liquid from said first chamber to said second chamber is a level control sensor within said second chamber. 
     
     
       28. An apparatus according to claim 18 wherein said means to deliver a bactericide-treated liquid to said media bed filter is a pump. 
     
     
       29. An apparatus according to claim 18 further comprising means to add a surfactant to said bactericide-treated liquid as said liquid is delivered to said filter. 
     
     
       30. A process for control of the quality of a media bed filter regenerating or backwashing liquid, to protect the filter bed media and the media support structure from the deleterious effects of biological solids generated or retained within said liquid comprising the steps of; (a) introducing a filtrate from said media bed filter plus a predetermined amount of bactericide into a first collection chamber with a removable screen assembly contained therein, to form a bactericide-treated filtrate;   (b) terminating the introduction of said filtrate and said bacteride to said first collection chamber upon said bactericide-treated filtrate reaching a predetermined upper level therein;   (c) regenerating or backwashing said media bed filter with said bactericide-treated filtrate from said first collection chamber which has traversed said screen assembly; and   (d) commencing the introduction of said filtrate and said bactericide to said first collection chamber upon said bactericide-treated filtrate dropping below said predetermined upper level therein.   
     
     
       31. A process according to claim 30 comprising the additional step of: (e) adding a surfactant to said bactericide-treated filtrate in step (c) to assist in regenerating or backwashing said media bed filter.   
     
     
       32. a process according to claim 30 wherein said filtrate and said bactericide in step (a) are mixed prior to entering said first collection chamber. 
     
     
       33. A process according to claim 30 wherein said predetermined amount of bactericide added to said filtrate in step (a) is determined by measuring said filtrate's flow with a meter. 
     
     
       34. A process according to claim 30 wherein said predetermined amount of bactericide added to said filtrate in step (a) is determined by the flow rate of a pump introducing filtrate to said first collection chamber. 
     
     
       35. A process according to claim 30 wherein said filtrate and said bactericide of step (a) are introduced into said first collection chamber exterior to said removable screen assembly and said bactericide-treated filtrate of step (c) is withdrawn from within said screen assembly. 
     
     
       36. A process according to claim 30 wherein said filtrate and said bactericide of step (a) are introduced into said first collection chamber within said removable screen assembly and said bactericide-treated filtrate of step (c) is withdrawn from exterior said screen assembly. 
     
     
       37. A process according to claim 30 wherein a resistance to said bactericide-treated filtrate traversing said screen assembly in said first collection chamber in step (c) produces an alarm signal. 
     
     
       38. A process according to claim 37 wherein said alarm signal is produced by a difference in the levels of bactericide-treated filtrate across said screen assembly exceeding a predetermined value. 
     
     
       39. An apparatus for control of the quality of a media bed filter regenerating and backwashing liquid, to protect the filter bed media and the media support structure from the deleterious effects of biological solids generated or retained within said liquid comprising; a first collection chamber with liquid inlet; a removable screen assembly contained therein; means for introducing liquid into said chamber; means for introducing a predetermined amount of bactericide into said chamber; control means for terminating introduction of liquid and bactericide into said chamber upon the liquid in said chamber reaching a predetermined level; means to deliver bactericide-treated liquid which has traversed said screen assembly to said media bed filter to regenerate or backwash said filter; and means to signal a resistance to bactericide-treated liquid traversing said screen assembly.   
     
     
       40. An apparatus according to claim 39 wherein said removable screen assembly is a rectangular box metalwork frame with a screen material mounted on four vertical sides and bottom of said frame, with an open top. 
     
     
       41. An apparatus according to claim 40 wherein said screen material contains openings no larger than the openings of a screen material supporting the filter bed media. 
     
     
       42. An apparatus according to claim 40 wherein said screen material contains openings smaller than the openings of a screen material supporting the filter bed media. 
     
     
       43. An apparatus according to claim 39 wherein said means for introducing liquid into said chamber is an outlet valve and a conduit which redirects filtrate from an outlet of said filter to said chamber. 
     
     
       44. An apparatus according to claim 43 wherein said means for introducing a predetermined amount of bactericide into said chamber is a pump controlled by a meter within said conduit which redirects filtrate from an outlet of said filter to said chamber. 
     
     
       45. An apparatus according to claim 43 wherein said control means for terminating introduction of liquid and bactericide into said chamber is a level switch which controls said outlet valve. 
     
     
       46. An apparatus according to claim 39 wherein said means to deliver a bactericide-treated liquid to said filter to regenerate or backwash said filter is a backwash pump and a conduit to said filter. 
     
     
       47. An apparatus according to claim 39 wherein said means to signal a resistance to bactericide-treated liquid traversing said screen assembly are upper and lower level sensors, one located interior said screen assembly and one located exterior said screen assembly with said upper level sensor located on the side of said screen assembly which receives said liquid and said bactericide. 
     
     
       48. An apparatus according to claim 39 wherein said means for introducing liquid into said chamber is a first pump which receives filtrate from said media bed filter. 
     
     
       49. An apparatus according to claim 48 wherein said means for introducing a predetermined amount of bactericide into said chamber is a second pump controlled by the operation of said first pump. 
     
     
       50. An apparatus according to claim 49 wherein said control means for terminating introduction of liquid and bactericide into said chamber is a level switch within said chamber which controls said first and said second pumps. 
     
     
       51. An apparatus according to claim 48 wherein said means to deliver bactericide-treated liquid which has traversed said screen assembly to said media bed filter to regenerate or backwash said filter is said first pump and a conduit to said filter. 
     
     
       52. An apparatus according to claim 39 further comprising means to add a surfactant to said bactericide-treated liquid as said liquid is delivered to said media bed filter.